Yes, HFC 134a is weaker then green gas, but good enough for a non metal slide pistol. it isn't TOO weak to. And any comprised gas cant be shipped by air, so if you consider getting something out of Canada keep that in mind.
But just use duster gas. Or get a flow restrictor which allows you to use propane in ur gun ( from MadMax @ Airsoft innovation
http://www.airsoft-innovations.com/i...ducts&id=AI-03 ) or just get a metal slide, and better internals.
I recommend the flow restrictor (cheap way of modding it to accept green gas, read over the link i sent you, or ask MadMax here, if you have other questions.) , but if you have the money get a metal slide for it, cuss it will look much better